The clinical efficacy of local nasal immunotherapy (LNIT) in patients with allergic rhinitis is amply documented. The aim of the study was to determine the effect on bronchial hyperresponsiveness (BHR) assessed at baseline and after 3 years of LNIT or pharmacological treatment alone. Forty-three randomized patients with allergic oculorhinitis were enrolled (26 positive to Graminaceae and 17 to Parietaria judaica pollens). All patients were asked whether they were willing to follow a 3-year treatment course involving preseasonal LNIT with a powder extract of Graminaceae or Parietaria pollens. Twenty-four patients (16 allergic to Graminaceae and eight to Parietaria) selected LNIT and the other 19 opted for symptomatic pharmacological treatment only. The latter was considered the control group. On the basis of positive or negative bronchial hyperresponsiveness and the LNIT, four subgroups were established and followed in open conditions, during which a record was kept of symptom scores, drug use, spirometry and methacholine test findings. After 3 years, patients treated with LNIT had a significant reduction of symptoms and drug intake. In the controls, symptoms worsened, thus requiring more drugs to control them. Bronchial hyperresponsiveness significantly improved in hyperreactive patients receiving LN7IT 10 of whom were no longer hyperreactive and one at a higher threshold. Among controls, bronchial hyperresponsiveness did not change, with the exception of three nonreactive patients who became hyperreactive, one of them with asthma. These findings confirm the efficacy of LNIT in allergic rhinitis suggesting that it might have systemic activity interfering with bronchial hyperresponsiveness and hence the onset of bronchial asthma.